1. Field of the Invention
The present invention relates to processes and systems for synthesizing alkyl bromides into high molecular weight hydrocarbons in at least two sequential or concurrent stages, and more particularly, in one or more embodiments, to processes and systems for synthesizing alkyl bromides in at least two sequential or concurrent stages operated with different feeds and at different temperatures.
2. Description of Related Art
Mono-brominated alkanes may be used in the production of high molecular weight hydrocarbons, such as C5+ gasoline-range and heavier hydrocarbons, as well as olefins, for example by conversion over an appropriate catalyst, such as a synthetic crystalline alumino-silicate catalyst, at sufficient temperatures to form high molecular-weight C3+ hydrocarbons, the C6+ fraction of which are predominately substituted aromatics. As the aromatic content of the C6+ fraction of the high molecular weight hydrocarbons derived from such a process is higher than desired for production of “neat” gasoline motor fuel, the C6+ fraction is valuable as a high-octane blending component with a petroleum-derived naphtha or natural gasoline derived from the processing of natural gas to produce a motor fuel. Petroleum-derived naphtha or natural gasoline derived from the processing of natural gas typically contain substantial paraffin content and have low octane ratings. Thus, a need exists for a process of synthesizing mono-brominated alkanes over a suitable catalyst and at a suitable temperature to produce higher molecular-weight C3+ hydrocarbons, the C6+ fraction of which contains a substantial C6+ paraffin content and thus a reduced aromatic content.
Poly-brominated alkanes, particularly di-brominated methane, tri-brominated methane, and mixtures thereof, are often formed during the bromination of lower molecular weight alkanes along with the preferred mono-brominated alkanes. The presence of these poly-brominated alkanes significantly increase the rate of coke formation during the conversion alkyl bromides over an appropriate catalyst as mentioned above. Such coke formation more rapidly deactivates the catalyst leading to short cycle times between regenerations and reducing the carbon efficiency of the process. Thus, a further need exists to significantly reduce the coke formation attributed to poly-brominated alkanes during the synthesis of mono-brominated alkanes and to increase the yield of higher molecular-weight C3+ hydrocarbons